Single Crystal Catalysts Research Articles

Acid-Base Cascades in Zeotype Single Crystal for Sugar Conversion.

The chemically catalyzed production of fructose syrup from high concentrations of glucose is crucial for the food industry and biorefining. In this work, a single crystal catalyst was synthesized via protective desilication of zeolite while incorporating indium. Glucose was isomerized in methanol at concentrations as high as 33 wt % before being hydrolyzed with water. The final fructose production was 54.9 %, with 89.1 % selectivity and 93.3 % sugar recovery, the highest isomerization rate at the highest concentration ever reported. Indium was present in the single-crystal catalyst as oxide nanoparticles and boundary framework atoms, and it achieved intelligent cooperation in the production of fructose syrup in methanol by catalyzing isomerization and selective glycosidation, minimizing degradation due to fructose accumulation and eliminating side reactions. This study contributed to the advancement of the industrial practice of chemically catalyzed glucose isomerization.

Acid‐Base Cascades in Zeotype Single Crystal for Sugar Conversion

AbstractThe chemically catalyzed production of fructose syrup from high concentrations of glucose is crucial for the food industry and biorefining. In this work, a single crystal catalyst was synthesized via protective desilication of zeolite while incorporating indium. Glucose was isomerized in methanol at concentrations as high as 33 wt % before being hydrolyzed with water. The final fructose production was 54.9 %, with 89.1 % selectivity and 93.3 % sugar recovery, the highest isomerization rate at the highest concentration ever reported. Indium was present in the single‐crystal catalyst as oxide nanoparticles and boundary framework atoms, and it achieved intelligent cooperation in the production of fructose syrup in methanol by catalyzing isomerization and selective glycosidation, minimizing degradation due to fructose accumulation and eliminating side reactions. This study contributed to the advancement of the industrial practice of chemically catalyzed glucose isomerization.

Modeling the Environment-Dependent Kinetics of Oxygen Reduction Reaction – a Continuum Model for Electric Double Layer

For proton-exchange-membrane fuel cells (PEMFCs) to achieve broad commercialization, improved energy-conversion efficiency with minimal Pt-based electrocatalyst is required [1]. Because the sluggish rate of oxygen reduction reaction (ORR) limits the efficiency of PEMFCs [2], the efficiency improvement requires a better understanding of ORR kinetics and mechanism to design better catalyst. To understand the ORR mechanism, theoretical and experimental analyses have been conducted. While previous studies reasonably explained the catalyst-dependent activity on single crystal catalysts in 0.1 M perchloric acid solution [3, 4], the explicit effect of electrolyte and related microenvironments [5, 6] is not thoroughly understood. The change in the electrolyte alters the electric-double-layer (EDL) structure and thus the local microenvironment at the electrode/electrolyte interface. Thus, the structure of the EDL should be carefully analyzed to uncover the electrolyte-dependent reaction kinetics. In this talk, we propose a multiscale continuum model to predict the EDL structure and examine the effect of perchloric acid concentration on ORR activity on Pt (111). The model includes Density Potential Functional Theory (DPFT) for electron density and Modified Poisson Boltzmann equation for species’ density and electric potential [7]. Also, the interaction between adsorbents and electric field is taken into account by minimizing the grand potential. After model validation with experimentally measured double-layer capacity data as a function of applied potential and concentration, the effect of the perchloric acid concentration (0.02 M – 0.2 M) on ORR activity is analyzed and discussed. It is shown that the model reproduces the specific activity obtained in the experiments when assuming the oxygen adsorption is limiting the rate, which can be attributed to the large energetic barrier for solvent reorganization [8]. Then, extension of the model to PEMFC ionomer electrolytes will be introduced. Overall, the model framework and findings provide insights into the ORR mechanism and guidance on how to tailor catalyst materials for increased PEMFC performance. Acknowledgements: This work was partially supported by the Hydrogen and Fuel Cell Technologies Office (HFTO), Office of Energy Efficiency and Renewable Energy, U.S. Department of Energy (DOE) through the Million Mile Fuel Cell Truck (M2FCT) consortia, technology managers G. Kleen and D. Papageorgopoulos, under contract number DE-AC02- 05CH11231, as well as by a CRADA with Toyota Central R&D Labs., Inc.. Reference [1] D. A. Cullen, K. C. Neyerlin, R. K. Ahluwalia, R. Mukundan, K. L. More, R. L. Borup, A. Z. Weber, D. J. Myers and A. Kusoglu, Nature Energy, 6, 462 (2021).[2] I. E. L. Stephens, A. S. Bondarenko, U. Grønbjerg, J. Rossmeisl and I. Chorkendorff, Energy & Environmental Science, 5 (2012).[3] M. Shibata, M. Inaba, K. Shinozaki, K. Kodama and R. Jinnouchi, Journal of The Electrochemical Society, 169 (2022).[4] H. A. Hansen, V. Viswanathan and J. K. Nørskov, The Journal of Physical Chemistry C, 118, 6706 (2014).[5] K. Kodama, K. Motobayashi, A. Shinohara, N. Hasegawa, K. Kudo, R. Jinnouchi, M. Osawa and Y. Morimoto, ACS Catalysis, 8, 694 (2017).[6] M. Luo and M. T. M. Koper, Nature Catalysis, 5, 615 (2022).[7] J. Huang, J Chem Theory Comput, 19, 1003 (2023).[8] D. T. Limmer, A. P. Willard, P. Madden and D. Chandler, Proceedings of the National Academy of Sciences, 110, 4200 (2013).

Enhanced Oxygen Evolution Activity and Stability of RuO2(110) Surface by Ti Doping

Introduction Developing highly active and durable electrocatalysts for the oxygen evolution reaction (OER) is essential for efficient hydrogen production through polymer electrolyte membrane water electrolysis (PEMWE). Although RuO2 exhibits the highest OER activity among pure transition metal oxide catalysts, its low durability hampers its practical application as an OER catalyst for PEMWE. Recent studies have shown that the incorporation of dissimilar metal elements, such as Ni, Mn, and Cu, effectively enhances the OER activity and stability of RuO2 in acidic electrolytes (1-3). In this study, we focus on Ti, a corrosion-resistant element in the PEMWE environment, and investigate the effects of doping amounts on the OER activity and stability of a RuO2(110) single crystal model catalyst surface. Experimental Non-doped rutile-type TiO2(110) single crystals were used as sample substrates. Ru and Ti, with a total thickness of 40 nm, were deposited onto the substrate at 400 ℃ under 0.5 Pa-O2 partial pressure using the arc-plasma deposition (APD) method. Subsequently, the sample was post-annealed at 400℃ for 1 hour in air using a tube furnace. Hereafter, the samples are denoted as RuO2-Tix (x represents the atomic percentage of doped Ti).Oxygen evolution activity was measured by linear sweep voltammetry (LSV) at a scan rate of 20 mV s-1 in N2-purged 0.1 M HClO4 at room temperature. Chronopotentiometry (CP) was conducted at 1 mA cm-2 for 120 min to evaluate the durability. The electrochemical impedance spectroscopy was conducted at 1.6 V vs. reversible hydrogen electrode (RHE) to measure the solution resistance. All the LSV and CP data were iR-corrected using the Rs values. Out-of-plane X-ray diffraction (XRD) analysis was carried out to evaluate the crystal structure. The dissolution amounts of Ru into the electrolyte after CP were evaluated by inductively coupled plasma mass spectrometry (ICP-MS). Results and Discussions Fig. 1(a) presents the out-of-plane XRD patterns of Ti-doped and non-doped RuO2(110) samples. The results indicate that (110)-oriented Ti-doped and non-doped RuO2 thin films were successfully obtained on TiO2 substrates. However, the peak position of RuO2(110) gradually shifts to the lower angle side, and the peak becomes less distinct with increasing Ti-doping amounts, suggesting that doped Ti is dissolved in the RuO2 crystal lattice and the crystallinity decreases with increasing doping amounts. Initial LSV curves for OER are shown in Fig. 1(b). The current density of RuO2-Ti4, 5, and 7 samples significantly increases at higher potential regions above 1.6 V vs. RHE, while RuO2-Ti2 and 10 exhibit decreased activity. The CP curves presented in (c) demonstrate that Ti doping, especially at 5 and 7 at.%, effectively suppresses the overpotential increase during CP. The dissolution amounts of Ru after 120 min of CP are summarized in (d). The dissolution amounts tend to decrease with increasing Ti-doping amounts. These results clearly show that an appropriate amount of Ti-doping effectively enhances both the OER activity and electrochemical stability of the RuO2(110) surface.AcknowledgmentsThis study was partly supported by JSPS KAKENHI Grant Number 21H01661, 22K19078 and Toyota Mobility Foundation Hydrogen Initiative. References Z. Y. Wu, F. Y. Chen, B. Li, S. W. Yu, Y. Z. Finfrock, D. M. Meira, Q. Q. Yan, P. Zhu, M. X. Chen, T. W. Song, Z. Yin, H. W. Liang, S. Zhang, G. Wang and H. Wang, Nat. Mater., 22, 100 (2023). S. Chen, H. Huang, P. Jiang, K. Yang, J. Diao, S. Gong, S. Liu, M. Huang, H. Wang and Q. Chen, ACS Catal., 10, 1152 (2020). J. Su, R. Ge, K. Jiang, Y. Dong, F. Hao, Z. Tian, G. Chen and L. Chen, Adv Mater, 30, 1801351 (2018). Figure 1

Single Crystal (K,Na)Nb)3/CuO Heterostructures for Synergistic Photo-Piezocatalytic Activity

In this study, we designed a heterostructure piezo-photocatalyst composed of Ba, Li doped- (K,Na)NbO3 (KNN) single-crystal microcuboids and CuO nanodots. KNN was selected because of its high piezoelectric coefficient (d33 ), good chemical stability, and environmental friendliness. As a cocatalyst, CuO was considered owing to its advantages such as narrow bandgap, low cost, and nontoxicity. The n-type semiconducting Pb-free KNN single-crystal ferroelectric microcuboids (~30 μm) were synthesized by molten-salt reaction. Then, p-type semiconducting CuO nanodots (less than 5 nm) were uniformly decorated onto KNN microcuboids via deposition of Cu(OH)2, followed by conversion to CuO through calcination. From our heterostructure, it is expected that excellent piezoelectric properties could be obtained from KNN single-crystal microcuboids and a high surface area for catalytic reactions is guaranteed by CuO nanodots that are evenly deposited on the surface of KNN without aggregation. The novel KNN/CuO micro/nano heterostructures exhibited increased current density, and enhanced removal organic dye (RhB) efficiencies under the ultrasonic vibration when compared with bare KNN single-crystal catalysts. Specifically, the reaction rate constant (k) for the photo-piezocatalytic RhB dye degradation of the KNN/CuO micro/nano heterostructure exhibited ~ 0.093 min-1, which is higher when compared with other KNN-based piezo, photo, and photo-piezocatalysts. Additionally, the coupled photo-piezocatalyst for KNN/CuO realized an enhanced RhB dye degradation efficiency of 1.6 times and 48.6 times higher when compared with individual piezocatalytic and photocatalytic dye degradation capabilities, respectively. Our approach could provide insights into the design of heterostructure photo-piezocatalysts containing single-crystal ferroelectrics, which requires the enhancement of the photo-piezocatalytic activities.

Br doping promotes the transform of Cu2O (100) to Cu2O (111) and facilitates efficient photocatalytic degradation of tetracycline

The activity of single-crystal catalysts with different crystal faces varies greatly, and the construction of catalysts with highly exposed active facets is essential for the improvement of photocatalytic performance. In this paper, Cu2O (100) crystal facets were transformed into high degrade-active Cu2O (111) crystal facets by doping with halogen atoms Br for the photocatalytic degradation of tetracycline. The effect of the optimal Br/Cu2O ratio on the degradation activity was investigated by adjusting the amount of Br. Meanwhile, based on photocatalytic degradation performance tests, photoelectric performance characterization and theoretical calculations, it was found that the doped Br-Cu2O introduced impurity energy levels, reduced the band gap, broadened the absorption range of the photocatalyst under visible light, and enhanced the oxidation capacity and the rate of photogenerated electron leap. In addition, the highly active Cu2O (111) crystal surface facilitates the adsorption of oxygen to generate superoxide radicals and promote the photocatalytic reaction. The synergistic effect of these two aspects promotes the efficient degradation of tetracycline by Br-Cu2O. This work provides a promising idea for the design and construction of highly efficient active surface highly exposed photocatalysts.

Direct C–C bond scission of xylitol to ethylene and propylene glycol precursors using single-atom catalysts (SACs) anchored on MgO

Shorter chain alcohols, as opposed to longer ones, are beneficial as biomass feedstock for chemicals and fuels, including hydrogen production. More so, it has been demonstrated that carbon–carbon rather than carbon–oxygen bond-cleaving activity determines the product selectivity of a metal catalyst for higher oxygenates reforming. In this report, we investigate the direct C2–C3 bond-cleaving activity of xylitol via first-principles, periodic density functional theory calculations to identify the differences in activities between single-crystal catalysts (SCCs) and single-atom catalysts (SACs). A comparison of the kinetic barriers revealed that xylitol's C–C bond scission appears to be a near-impossible task on SCCs. However, SACs demonstrated higher performance. For example, Ir1/MgO and Ir1/MgO_Ovac (having surface oxygen vacancy) yielded ∼72% and 54% decrease, respectively, in Gibb’s free activation energy compared to Ir (111) at the xylitol reforming operating temperature of 473 K. Furthermore, electronic structure calculations revealed an up-shift in the DOS for the surface M1 atoms in all investigated SACs compared to the surface atoms of their respective SCCs, resulting in M1 higher d-band center and stronger adsorbate (s) binding. This study highlights the importance of SACs for boosting the atom efficiency of costly metals while also offering a new strategy for tuning the activity of catalytic reactions.

Structural and Composition Evolution of Palladium Catalyst for CO Oxidation under Steady-State Reaction Conditions

Understanding how the composition and structure of heterogeneous catalysts change during in situ reaction is of critical importance but greatly challenging because of the complexity of multiple time–space scale. Herein, we propose a self-adaptive simulation strategy driven by the first-principles microkinetic modeling and genetic-algorithm-based global structural search accelerated by machine learning that allows the interplay of surface reaction and catalyst evolution, and uncover the structural/compositional evolution of a Pd(111) single-crystal catalyst under the reaction conditions for CO oxidation, which is a classic open problem lasting for decades. The possible active phases at the kinetically steady state are identified and their common nature is unraveled. We show that, in the presence of CO/O2 reaction mixtures, a dynamically stable partially oxidized nonstoichiometric palladium oxide (PdO0.44 layer) grown on Pd(111) is formed with the O adatoms inserted into the Pd(111) sublayer that drives the formation of the surface oxide. Remarkably, the first-principles microkinetic analyses demonstrate that this self-evolved PdO0.44 surface at the steady state exhibits higher catalytic activity for CO oxidation as compared with Pd(111) and overoxidized PdO catalyst, which may explain the long-standing puzzle of the “PdOx” active phase for Pd catalyst during CO oxidation.

Uniform Catalytic Nanocrystals: From Model Catalysts to Efficient Catalysts

ConspectusSolid catalysts play a key role in the chemical industry, energy, and the environment. Fundamental understanding of heterogeneous catalysis exerted by solid surfaces is useful for structural designs of efficient catalysts but is challenging due to the complexity. Emerging uniform catalytic nanocrystals (NCs) with controlled and well-defined surface structures have brought new opportunities for fundamental understanding and directed explorations of efficient catalysts. In a previous Account ( Acc. Chem. Res. 2016, 49, 520−527), I postulated and exemplified a concept of oxide nanocrystal model catalysts for the fundamental investigations of oxide catalysis without the “materials gap” and “pressure gap” which are often encountered using the traditional single crystal model catalysts. In this Account, I summarize our effort in fabricating efficient uniform nanocrystal catalysts based on the fundamental understanding of structure–activity relations and reaction mechanisms acquired by oxide nanocrystal model catalyst studies. Directed by the fundamental understanding that the Cu2O{110} facet is active in catalyzing propylene epoxidation with O2 and the fine Cu2O nanocube exposes high densities of Cu2O{110} edge sites, we successfully explore fine Cu2O nanocubes as a highly selective catalyst for propylene epoxidation with O2. Directed by the fundamental understanding that the Cu{100} facet is the active Cu facet in catalyzing the water–gas shift (WGS) reaction, we successfully fabricate a highly active ZnO/fine Cu nanocube WGS catalyst with enhanced ZnO-CuCu{100} active site density. Directed by the fundamental understanding of TiO2 facet effects on the surface band bending and adsorbate–surface interfacial energy level alignment, and consequent photocatalytic performance, we successfully fabricate highly active TiO2{001} NC-based photocatalysts for photocatalytic CH4 conversions. These results adequately exemplify the concept of fundamental understanding-directed explorations of efficient catalysts following a strategy of “identification of active site structure + maximization of active site density”, which, together with the advancement of controlled-synthesis methods, is expected to greatly accelerate the explorations of novel and efficient catalysts in future.

Water Formation Kinetics on Co(0001) at Low and Near-Ambient Hydrogen Pressures in the Context of Fischer–Tropsch Synthesis

Understanding the kinetics of oxygen removal from catalytically active metal surfaces by hydrogen is important for several catalytic reactions such as Fischer–Tropsch synthesis, methanation of CO or CO2, and the reverse-water–gas-shift reaction. Motivated by FTS, a Co(0001) single crystal model catalyst was used to study the kinetics of oxygen removal through reaction with hydrogen. Kinetic studies in the 10–7–10–4 mbar H2 pressure regime show that water formation is first order in the surface hydrogen concentration while the order in oxygen concentration changes from one at low oxygen coverage to zero at high oxygen coverage. In situ XPS shows that the hydrogen surface concentration saturates around 10–1 mbar and on this basis the typical temperature of 450 K needed for water formation in this pressure regime can be considered as typical for high pressures as well. The absence of OH buildup during the reaction points to O + H as the rate-limiting step, with a barrier of ∼120 kJ mol–1. Such a high barrier shows that slow removal of adsorbed oxygen from the surface of reactive metal catalysts such as cobalt may be rate-limiting for the overall reaction.

Observation of a robust and active catalyst for hydrogen evolution under high current densities

Despite the fruitful achievements in the development of hydrogen production catalysts with record-breaking performances, there is still a lack of durable catalysts that could work under large current densities (>1000 mA cm−2). Here, we investigated the catalytic behaviors of Sr2RuO4 bulk single crystals. This crystal has demonstrated remarkable activities under the current density of 1000 mA cm−2, which require overpotentials of 182 and 278 mV in 0.5 M H2SO4 and 1 M KOH electrolytes, respectively. These materials are stable for 56 days of continuous testing at a high current density of above 1000 mA cm−2 and then under operating temperatures of 70 °C. The in-situ formation of ferromagnetic Ru clusters at the crystal surface is observed, endowing the single-crystal catalyst with low charge transfer resistance and high wettability for rapid gas bubble removal. These experiments exemplify the potential of designing HER catalysts that work under industrial-scale current density.

Modeling the Environment-Dependent Kinetics of Oxygen Reduction Reaction – Effect of Relative Humidity

For proton exchange membrane fuel cells (PEMFCs) to achieve broad commercialization, the kinetics of oxygen reduction reaction (ORR) need to be better understood to improve the efficiency with minimized use of expensive Pt-based electrocatalyst(1). The increasing demands of PEMFC-powered heavy-duty vehicles make this issue critical, especially to meet the efficiency target (ultimately 72%)(2). Previous first principle-based theoretical analyses reasonably explained catalyst-dependent activity in ideal conditions (on single crystal catalysts in HClO4 solution under room temperature)(3). To design a practical catalyst, further analysis is required to bridge the gap between the ideal and actual PEMFC conditions (typically, covered with perfluorosulfonic acids under 60 to 90 °C, and 30 to 100% RH). In this talk, we examine the effect of relative humidity (RH) on ORR activity on a platinum surface. The effect of RH on ORR activity has been a controversial topic: an experimental study suggested lower RH increases the ORR activity(4), while another study showed the opposite trend(5). By using a multiscale continuum model, we validate our hypothesis that the controversial experimental results stem from the difference in the properties of the electrode/electrolyte interface. In the mathematical calculation, we assume that the polycrystalline platinum catalysts consist of multiple single crystalline surfaces(6) and that their activity is described by the summation of the activities on the single crystalline surfaces. Based on transition state theory, the reaction rate of each elementary step is calculated from the reaction free energy, reactant concentration, and activation energy with explicit accounting of the double-layer structure and interactions. In the presentation, the calculation results will be compared with experimental solid-state data using microelectrodes, and the mechanism of RH-dependent ORR activity will be discussed. Reference I. E. L. Stephens, A. S. Bondarenko, U. Grønbjerg, J. Rossmeisl and I. Chorkendorff, Energy & Environmental Science, 5 (2012).D. A. Cullen, K. C. Neyerlin, R. K. Ahluwalia, R. Mukundan, K. L. More, R. L. Borup, A. Z. Weber, D. J. Myers and A. Kusoglu, Nature Energy, 6, 462 (2021).H. A. Hansen, V. Viswanathan and J. K. Nørskov, The Journal of Physical Chemistry C, 118, 6706 (2014).M. Shibata, M. Inaba, K. Shinozaki, K. Kodama and R. Jinnouchi, Journal of The Electrochemical Society, 169, 044507 (2022).H. Xu, Y. Song, H. R. Kunz and J. M. Fenton, Journal of The Electrochemical Society, 152 (2005).G. A. Tritsaris, J. Greeley, J. Rossmeisl and J. K. Nørskov, Catalysis Letters, 141, 909 (2011).

(Digital Presentation) Oxygen Evolution Activity of RuO2/MO2/TiO2(110) (M = Ir, Sn) Surfaces in Acidic Electrolyte

Introduction Developing highly active and durable electrocatalysts for oxygen evolution reaction (OER) are required for efficient hydrogen production by polymer electrolyte membrane water electrolysis (PEMWE). While RuO2 shows the highest OER activity among pure transition metal oxides catalysts, the low durability hinders its practical application as OER catalyst for PEMWE. Recent studies demonstrated that RuO2 mixed with other metal oxides, such as IrO2 and SnO2 etc. showed higher activity and durability than pure RuO2 (1-3). When the RuO2 deposited on the other metal oxides, interfacial resistance and lattice strain which derives from the lattice mismatch should influence on the OER properties. In this study, to clarify the influence of interface between different rutile-type oxides, we fabricated RuO2/MO2/TiO2(110) (M = Ir or Sn) single crystal model catalyst and evaluated the oxygen evolution activity and durability. Experimental Nb-doped TiO2(110) (Nb: 1 wt%) single crystal substrate was etched in 20 % HF solution for 10 min and annealed at 1000 ℃ in air. After the sample transfer to the APD chamber, 2 nm-thick Ir or Sn was deposited onto the substrate at room temperature under 0.5 Pa-O2 partial pressure and annealed at 350 ℃ for 30 min under the same O2 pressure. After that, 4 nm-thick Ru was deposited on the MO2/TiO2(110) and was annealed under the same condition of the MO2 layer. Hereafter, the sample was denoted as RuO2/MO2/TiO2.Oxygen evolution activity was measured by linear sweep voltammetry (LSV) at a scan rate of 1 mV/s in N2-purged 0.1 M HClO4 at room temperature. The electrochemical impedance spectroscopy was conducted at 1.5 V vs. reversible hydrogen electrode (RHE) to measure the resistance of solution (Rs), electrodes (Re), and charge transfer for OER (Rct). The LSV curves were corrected using the measured Rs. Chronopotentiometry was conducted at 0.5 mA/cm2 for 120 min to evaluate the durability. In-plane XRD analysis was performed for estimating lattice strain in the surface RuO2 layer. Results and Discussions XRD analysis showed that both of the MO2 interlayer and RuO2 catalyst layer grow with (110) orientation on the TiO2(110) substrate. Figure 1(a) shows initial LSV curves for OER. The onset potential of RuO2/SnO2/TiO2 samples clearly shifted to lower potential side relative to the RuO2/IrO2/TiO2 and RuO2/TiO2 samples. The overpotential at 0.1 mA cm-2 of the RuO2/SnO2/TiO2 (b) was ca. 25 mV lower than the other two samples. The chronopotentiometric curves (c) showed the overpotential of RuO2/TiO2 increased by 250 mV after 120 min. On the other hand, change in the overpotential of the RuO2/SnO2/TiO2 was only 25 mV, indicating the high durability.Cole-cole plots at 1.5 V (d) revealed that both of the Re and Rct were significantly reduced owing to SnO2 interlayer, while the IrO2 layer slightly increased the Re and decreased the Rct. In-plane XRD results showed the compressive lattice strain was induced in [001] direction in RuO2 layer on TiO2 substrate and decreased by insertion of IrO2 and SnO2 layer. However, the lattice spacing in [-110] direction was almost the same for all the samples. Figure 1 (e) shows the relation between Rct and the lattice strain in [001] direction. The Rct tended to decrease with decreasing the compressive strains, suggesting the OER activity of RuO2(110) surface is related to the anisotropic strains in [001] direction. The results demonstrated that the activity and durability of RuO2/TiO2 catalysts can be improved by insertion of SnO2 layer at the catalyst/substrate interface.AcknowledgmentsThis study was partly supported by JSPS KAKENHI Grant Number 21H01661 and Toyota Mobility Foundation Hydrogen Initiative. References R. V. Genova-Koleva, F. Alcaide, G. Álvarez, P. L. Cabot, H.-J. Grande, M. V. Martínez-Huerta and O. Miguel, Journal of Energy Chemistry, 34, 227 (2019).J. Li, X. Qin, G. Chen and G. Chen, Journal of the Taiwan Institute of Chemical Engineers, 125, 186 (2021).R. Samanta, P. Panda, R. Mishra and S. Barman, Energy & Fuels, 36, 1015 (2022). Figure 1

Structure Matters: Asymmetric CO Oxidation at Rh Steps with Different Atomic Packing.

Curved crystals are a simple but powerful approach to bridge the gap between single crystal surfaces and nanoparticle catalysts, by allowing a rational assessment of the role of active step sites in gas-surface reactions. Using a curved Rh(111) crystal, here, we investigate the effect of A-type (square geometry) and B-type (triangular geometry) atomic packing of steps on the catalytic CO oxidation on Rh at millibar pressures. Imaging the crystal during reaction ignition with laser-induced CO2 fluorescence demonstrates a two-step process, where B-steps ignite at lower temperature than A-steps. Such fundamental dissimilarity is explained in ambient pressure X-ray photoemission (AP-XPS) experiments, which reveal partial CO desorption and oxygen buildup only at B-steps. AP-XPS also proves that A-B step asymmetries extend to the active stage: at A-steps, low-active O–Rh–O trilayers buildup immediately after ignition, while highly active chemisorbed O is the dominant species on B-type steps. We conclude that B-steps are more efficient than A-steps for the CO oxidation.

Advances in facet-dependent photocatalytic properties of BiOCl catalyst for environmental remediation

Abstract Bismuth chloride oxide (BiOCl) is a typical V-VI-VII ternary oxide material, which is one of the widely studied metal oxides due to its unique surface, electronic and photocatalytic properties. However, the broad bandgap and the large number of photogenerated electron-hole pair complexes of BiOCl limit its photocatalytic efficiency. Since the photocatalytic performance of BiOCl is highly dependent on its exposed crystallographic facets, research attention has increasingly focused on the different structures and properties possessed by different crystallographic facets of BiOCl. This article reviews the basic principles of using different crystalline surfaces of BiOCl materials to enhance photocatalytic activity, summarizes the applications of BiOCl single-crystal catalysts and composite catalysts in the environmental field, and provides an outlook on the challenges and new research directions for future development in this emerging frontier area. It is hoped that the crystalline surface-related photocatalysis of BiOCl can be used to provide new guidance for the rational design of novel catalysts for various energy and environment-related applications.

Cu2O Nanocrystal Model Catalysts

Comprehensive SummaryModel catalysts approach is widely adopted in fundamental studies of complex heterogeneous catalysis. Traditional model catalysts are single crystal‐based model catalysts, whose results, however, sometimes suffer from the “material gap” and “pressure gap” when applied to working catalysts. Recently, uniform catalytic nanocrystals with well‐defined structures have emerged, and we have put forward a concept of nanocrystal‐based model catalysts for fundamental studies of complex heterogeneous catalysis under conditions approaching working catalysts as closely as possible. In this perspective, we summarize our research progresses on Cu2O‐based nanocrystal model catalysts. Following a brief introduction, we summarize controlled synthesis of uniform Cu2O nanocrystals with various morphologies, morphology‐dependent surface compositions and structures and surface chemistry of uniform Cu2O nanocrystals, and heterogeneous catalysis of Cu2O‐based nanocrystals. Finally, we conclude the concept of nanocrystal‐based model catalysts and outlook that uniform nanocrystals can act not only as model catalysts but also as efficient catalysts. What is the most favorite and original chemistry developed in your research group?By far, the most favorite and original chemistry developed in my research group is the concept of “nanocrystal model catalysts”, which overcomes the so‐called “materials gap” and “pressure gap” encountered by the research field of surface chemistry for heterogeneous catalysis using traditional single crystal model catalysts.How do you get into this specific field? Could you please share some experiences with our readers?Surface chemistry studies of single crystal model catalysts had been considered to be able to achieve the fundamental understanding of complex heterogeneous catalysis before the “materials gap” and “pressure gap” were found to exist between single crystal model catalysts and working powder catalysts. Since then, to overcome the “materials gap” and “pressure gap” has been a main goal of the research field of surface chemistry for heterogeneous catalysis. I established my research group in 2004 when catalytic nanocrystals with uniform and well‐defined surface structures emerged quite a lot, and then had the idea of using nanocrystals as a novel type of model catalysts for fundamental studies of complex heterogeneous catalysis under conditions approaching workingcatalysts as closely as possible. Our work has successfully validated the concept of “nanocrystal model catalysts”. Therefore, my experience is to bear the important problems of the research field in mind and keep learning new knowledge from related research fields.What is the most important personality for scientific research?In my personal opinion, intuitivism, persistence, and self‐motivation are the most important personalities for scientific research.What is your favorite journal(s)?I prefer to publish my papers in journals that have large readerships so that the reported new knowledge can be widely shared.What are your hobbies? What's your favorite book(s)?My hobbies are the things that do not need thinking and special attention. These things make me truly relaxed. My favorite books are history of science with comments written by famous scientists (translated) in Chinese.If you have anything else to tell our readers, please feel free to do so.Scientific research is full of inter‐transformed frustration and happiness, but allows one to demonstrate the intelligence and capability freely and independently.

Carbene-like reactivity of methoxy groups in a single crystal SAPO-34 MTO catalyst

In situ synchrotron infrared microspectroscopy on single crystals of SAPO-34 reveals that a carbene insertion mechanism is responsible for the first carbon–carbon bond formation from surface methoxy groups.

Magnetocatalysis: The Interplay between the Magnetic Field and Electrocatalysis

Magnetocatalysis: The Interplay between the Magnetic Field and Electrocatalysis

Integrated Wafer Scale Growth of Single Crystal Metal Films and High Quality Graphene.

We report on an approach to bring together single crystal metal catalyst preparation and graphene growth in a combined process flow using a standard cold-wall chemical vapor deposition (CVD) reactor. We employ a sandwich arrangement between a commercial polycrystalline Cu foil and c-plane sapphire wafer and show that close-spaced vacuum sublimation across the confined gap can result in an epitaxial, single-crystal Cu(111) film at high growth rate. The arrangement is scalable (we demonstrate 2″ wafer scale) and suppresses reactor contamination with Cu. While starting with an impure Cu foil, the freshly prepared Cu film is of high purity as measured by time-of-flight secondary ion mass spectrometry. We seamlessly connect the initial metallization with subsequent graphene growth via the introduction of hydrogen and gaseous carbon precursors, thereby eliminating contamination due to substrate transfer and common lengthy catalyst pretreatments. We show that the sandwich approach also enables for a Cu surface with nanometer scale roughness during graphene growth and thus results in high quality graphene similar to previously demonstrated Cu enclosure approaches. We systematically explore the parameter space and discuss the opportunities, including subsequent dry transfer, generality, and versatility of our approach particularly regarding the cost-efficient preparation of different single crystal film orientations and expansion to other material systems.

Significance of the Mn-Oxidation State in Catalytic and Noncatalytic Promotional Effects of MnOx Domains in Formic Acid Dehydrogenation on Pd/MnOx Interfaces

Influence of MnOx overlayers/nanoclusters deposited on the Pd(111) single crystal model catalyst surface on the catalytic dehydrogenation of double-deuterated formic acid (FA, DCOOD) was studied un...